The present invention relates to apparatus and a system for determining the integrity of sealed containers. The invention has specific application to parenteral pharmaceutical products which are typically packaged in rigid glass containers sealed with a combination rubber and metal closure.
Such pharmaceutical products are usually packaged by high speed automatic filling and capping equipment. The containers or bottles are filled with the medicament at a filling station and thereafter the closure assembly consisting generally of a rubber sealing element and an aluminum cup-like cap is placed over the discharge end of the container. The capping apparatus then applies a predetermined force to the cap to seat the closure assembly and then crimps the lower edge of the skirt of the cap under or around the bottle finish or flange to seal the container. Proper sealing for medicaments is important to prevent exposure to air or loss by evaporation and also to protect the contents from microbiological or other contamination.
It has been found that some containers packaged by mass production techniques are not adequately sealed. For a given cap, sealing element and container assembly, the seal is controlled primarily by the capping equipment. The capping equipment is initially set to apply a predetermined force to effect the proper seal. Thus if the initial setting of the capping machine is incorrect then the seal produced may be inadequate. Even if the initial setting of the capping equipment is correct, the setting may require adjustment by the operator from time to time and if these changes are inadvertently overlooked, this also may result in containers which are inadequately sealed. Inadequate seals may also result due to the fact that occasionally the various elements of the container assembly combine to comprise a specific assembly with extreme dimensional variation from the mean. This is a statistically predictable occurrence often seen in mechanical assemblies, even though the dimensions of the individual elements are within specified tolerances. Ordinarily, the seal is satisfactory so long as the combined dimension does not depart excessively from the desired mean value. However, in a given instance, if the combined dimension is at a statistical extreme, the seal produced may be unacceptable.
At present the seal integrity is first checked visually and then usually checked further by selecting containers periodically from the assembly line and inspecting them manually by attempting to turn the cap relative to the container.
If the cap does not rotate under the manual force applied, the seal is considered adequate. Such a method is inherently imprecise and subjective since it depends on the strength and judgment of the tester, which may vary from person to person and day to day.
With the foregoing in mind, the present invention is designed to provide apparatus and a system which measures a physical characteristic of the sealed closure system objectively in a manner so that it can be readily and accurately replicated and correlated to the integrity of the seal.
The present invention also provides apparatus and system for checking seal integrity even when the combined dimensional variations in the elements of the container cause it to fall outside the acceptable tolerance range.
Accordingly, it is an object of the present invention to provide a new and useful apparatus and system for checking the seal integrity of a sealed container employing a resilient rubber sealing element.
It is also an object of the present invention to provide such apparatus and system wherein the percent compression of the resilient sealing element can be checked relatively accurately.
It is still another object of the invention to provide a method and apparatus adapted to testing the integrity of seals on either a spot check basis, or on a statistically significant sampling, or on a 100% basis on which every unit is tested.
Another object is to provide such an apparatus and system which is simple, inexpensive and accurate.
A still further object of the present invention is to provide a novel apparatus and system capable of checking seal integrity for different types of closures utilizing a resilient sealing element.
Still another object of the present invention is to provide apparatus and system for checking seal integrity which may be used by operators with minimal skills and still provide accurate results. A further object of the present invention is to provide apparatus and system for checking seal integrity wherein localized engagement of the sensing head and top of the cap ensures accurate pre-seal and post-seal readings and avoids error which may be introduced as a result of "doming" of the center portion of the cap during the sealing operation and wherein the force exerted by the sensing head on the top of the cap is constant for all stroke positions of sensing head on the actual tester.